# International Workshop on Linear Colliders 2010 IWLC2010ABSTRACTS

Number of abstracts: 24

## Tracking and Vertexing

### Layout optimisation for the vertex and forward-tracking region in the CLIC-ILD and CLIC-SiD detector concept

• Speaker: Dominik Dannheim (CERN)

• Session: Tracking & Vtx, Vertex detectors, Wednesday 20-Oct-2010, 16:30 - 18:30

• Status: submitted 22-Sep-2010, accepted 16-Oct-2010

• Abstract:
The beam parameters of the proposed CLIC concept for a linear electron-positron collider with a centre-of-mass energy of up to 3 TeV pose challenging demands for the design of the vertex and forward-tracking detector regions. The layer placement as well as the temporal and spatial readout granularity are severely constrained by the high rates of beam-induced backgrou4nd events in the vicinity of the interaction region. The physics program of CLIC requires an excellent track-momentum resolution and efficient tagging of long-lived states through the identification of secondary vertices. Moreover, many important physics channels at 3 TeV centre-of-mass energy are strongly peaked in the forward regions of the detector, where also most of the beam-induced background events are expected. Therefore special attention has to be paid to the transition region from the vertex detector to the outer forward-tracking region. We present optimisation studies for two initial detector layouts based on the two approved ILC detector concepts ILD and SiD, respectively. Simulations of the Detector response have been used to investigate the main detector parameters and their interplay: Momentum and impact-parameter resolutions, track-finding efficiency, occupancies and background rejection. These parameters have been investigated as function of the number and placement of detector layers, their single-point resolutions and the material budget. The two proposed initial layouts will be used and further validated with a large-scale production and analysis of selected signal and background processes for the CLIC conceptual design report to be submitted in 2011.

### SiD tracking performance at CLIC

• Speaker: Blai Pie Valls (University of Barcelona)

• Session: Tracking/Vtx, Thursday 21-Oct-2010, 9:00 - 10:30

• Status: submitted 22-Sep-2010, accepted 16-Oct-2010

• Abstract:
The Silicon Detector Concept (SiD) was developed for the International Linear Collider (ILC) and has been validated. We present the tracking performance of a slightly modified SiD concept at CLIC energies as well as the impact of the machine-induced-backgrounds.

### Studies for a TPC in a CLIC Detector

• Speaker: Martin Killenberg (CERN)

• Session: Tracking & Vtx, TPC, Wednesday 20-Oct-2010, 16:30 - 18:30

• Status: submitted 22-Sep-2010, accepted 16-Oct-2010

• Abstract:
A TPC at the CLIC accelerator has to face high background and high track multiplicities in dense jets. We present the tools for a detailed simulation study which will answer the questions whether a TPC can handle a full bunch train including all background, and provide the required spatial resolution and track separation. The TPC measures the z coordinate as time since the beginning of the bunch train. In combination with a silicon detector, which measures the absolute position, it is possible to determine the time offset with respect to the beginning of the bunch train and thus determine the bunch crossing. With a resolution of order 150 µm a time resolution of 2 to 3 ns is possible, depending on the drift velocity. The talk gives a status report of these studies and shows first results.

### Design status of the Timepix2 pixel detector chip

• Speaker: Xavier Llopart Cudie (CERN)

• Session: Tracking & Vtx TPC, Wednesday 20-Oct-2010, 9:00 - 10:30

• Status: submitted 5-Oct-2010, accepted 16-Oct-2010

• Abstract:
Building on the success of the Timepix chip a new version of the chip is being designed in a commercial CMOS 130nm technology. The new chip will have the same dimensions as its predecessor: 55 um square pixels and 256 x 256 pixel matrix. Each pixel will record simultaneously the energy and arrival time information of detected events. The chip will be readout using a sparse readout data push architecture.

• Speaker: Paul Aspell (CERN)

• Session: Tracking & Vtx TPC, Wednesday 20-Oct-2010, 9:00 - 10:30

• Status: submitted 6-Oct-2010, accepted 16-Oct-2010

• Abstract:
The Saltro is a natural development of the ALICE TPC architecture integrating front-end amplification, analog to digital conversion and digital signal processing on the same chip. After a brief introduction the talk will focus on the present Saltro demonstrator design before moving onto projections for future chip possibilities with respect to technology, number of channels, power consumption and power management.

## Calorimetry and Muons

### Comparison of the Performance of Tungsten and Steel Hadronic Sampling Calorimeters

• Speaker: Peter Speckmayer (CERN)

• Session: Calo, Thursday 21-Oct-2010, 9:00 - 10:30

• Status: submitted 22-Sep-2010, accepted 10-Oct-2010

• Abstract:
The performance of tungsten and steel hadronic sampling calorimeters is shown using GEANT4 simulations. Various configurations with different sampling ratios and total calorimeter lengths for both materials have been investigated. Pions of up to 300GeV have been simulated in all configurations and the energy has been reconstructed using a neural network. An optimal configuration depending on the HCAL size has been determined.

### Studies of the CLIC HCAL depth with Pandora PFA

• Speaker: Angela Lucaci-Timoce (CERN)

• Session: Calo, Thursday 21-Oct-2010, 9:00 - 10:30

• Status: submitted 22-Sep-2010, accepted 10-Oct-2010

• Abstract:
In view of the CLIC Conceptual Design Report, the geometry of the CLIC detector needs to be fixed. To choose an optimum depth of the W-based HCAL, studies with different lengths (from 4 to 10 interaction lengths) were performed. Events with jets from Z->uds events, with energies from 45.5 to 1500 GeV were simulated with Mokka, and submitted to the GRID via DIRAC. After the reconstruction of events, an optimal depth of the calorimeter was chosed based on the jet energy resolution obtained with the Pandora PFA algorithm.

### Impact of the shower time evolution for a Tungsten based HCAL

• Proposed Speaker: Mark Thomson (University of Cambridge)

• Proposed Session: Calorimetry

• Status: submitted 28-Sep-2010

• Abstract:
The impact of the time structure of hadronic showers from single particles and jets in a W-Scintillaor calorimeter has been studied using Mokka GEANT4 detector simulation. The performance of such a calorimeter as a function of the timing cuts/windows applied to the HCAL will be presented and the implications for the timing requirements for a W-based HCAL at CLIC will be discussed.

### Investigation of the Time Structure of Showers in a Tungsten HCAL

• Speaker: Frank Simon (MPI Munich)

• Session: Calo, Thursday 21-Oct-2010, 14:00 - 15:30

• Status: sent to CALICE for approval 22-Sep-2010, submitted via CALICE, accepted 10-Oct-2010

• Abstract:
Due to its extremely high density, Tungsten is an attractive material for the absorber of the hadronic calorimeter of a CLIC detector. However, the heavy nucleus leads to increased nuclear processes which produced neutrons or a delayed emission of photons, resulting in an extended time structure of hadronic showers in such a calorimeter. At CLIC, a high background from hadrons produced by two photon processes is expected, which, coupled with the 0.5 ns bunch crossing frequency of the accelerator, imposes strict requirements on the timing capabilities of all detector systems to mitigate its influence. The time structure of the shower development in tungsten is likely a driving factor for the possible time resolution of the hadronic calorimeter. To study the suitability of a tungsten calorimeter with scintillator readout for CLIC, a test beam campaign with a 30 layer prototype using the CALICE AHCAL active elements is in preparation. In addition to this, a small number of scintillator cells directly read out with silicon photomultipliers and coupled to fast digitizers with deep buffers will be installed in the setup. These devices allow the measurement of the time structure of the signal in the scintillator with sub-ns resolution over several us, and will provide first insights into the time properties of hadronic showers in Tungsten. We will outline the time stamping requirements for a calorimeter at CLIC, discuss the present status of simulations and the prospects for a first measurement of the time structure and present first results from the commissioning of the test beam setup with muons.

### CALICE Tungsten HCAL Prototype status

• Speaker: Erik van der Kraaij (CERN)

• Session: Calo, Thursday 21-Oct-2010, 14:00 - 15:30

• Status: sent to CALICE for approval 20-Sep-2010, submitted via CALICE, accepted 10-Oct-2010

• Abstract:
Recently the CALICE hadronic calorimeter test setup was installed at CERN using 1cm thick tungsten plates as absorber material and scintillator tiles as readout system. It is now being commissioned in a muon beam and will be moved in November to the T9 testbeam line at the CERN-PS (1-10GeV/c). The goal of the test is to prove the technology of using tungsten as absorber material in an hadronic calorimeter, and to validate hadronic shower simulations at the required level of precision for detector optimization studies. In this talk we present the progress of the commissioning and its first results.

### Performance of Muon identification in Pandora PFA

• Speaker: Erik van der Kraaij (CERN)

• Session: Calo, Wednesday 20-Oct-2010, 9:00 - 10:30

• Status: submitted 22-Sep-2010, accepted 10-Oct-2010

• Abstract:
The muon system of a CLIC detector will have two roles. Firstly it will identify muons, coming either from the IP or crossing the detector as halo muons. Secondly, it will operate as a tail-catcher for very energetic jets. In this talk we first discuss the ongoing optimization of the layer geometry in the magnet yoke. We then present the performance of a new algorithm in Pandora, which is to identify muons at an early stage in the particle flow algorithm by fitting TPC tracks immediately to tracks in the muon system.

## Detector Performance and Software Tools

### Study of a 5T large aperture coil for the CLIC detector

• Speaker: Benoit Cure (CERN)

• Session: * Accelerator session: WG 5 (Interaction region, ATF2 and MDI)*, Thursday 21-Oct-2010, 16:00 - 18:00

• Status: submitted 22-Sep-2010, accepted 6-Oct-2010

• Abstract:
In the present design of a CLIC detector, a 6m diameter superconducting coil is requested to get a central induction of 5T. This presentation will give the main parameters of such a coil and will show the feasibility based on and compared to the CMS and Atlas central solenoid coil designs, indicating the limits on the conductor and the identified R&D prospects. The last computational results of the proposed structure will be presented.

### Simulation Studies regarding Beam-Beam Background in a CLIC Detector

• Speaker: Andre Sailer (CERN and Humboldt University of Berlin)

• Session: Detector Performance & software tools/Detector integration with MDI, Thursday 21-Oct-2010, 11:00 - 12:30

• Status: submitted 22-Sep-2010, accepted 6-Oct-2010

• Abstract:
A large amount of electron-positron pairs will be produced through beam-beam effects during the collisions at a linear collider. At larger energies particles produced through a coherent process, the so called trident cascade, will cause additional background in the detector. Background studies with GuineaPig and the Geant4 based Mokka simulation will be presented.

### Event Generation of gamma gamma -> hadrons

• Speaker: Tim Barklow (SLAC)

• Session: Detector Performance & software tools/Detector integration with MDI, Thursday 21-Oct-2010, 11:00 - 12:30

• Status: submitted 22-Sep-2010, accepted 6-Oct-2010

• Abstract:
The generation of gamma gamma -> hadrons background events at CLIC is reviewed. Kinematic cuts in event generation and event properties are examined. The guinea-pig generation of gamma gamma -> hadrons is compared with a similar event generation program developed at SLAC.

### A tau reconstruction algorithm for high energies at CLIC

• Speaker: Astrid Münnich (CERN)

• Session: Detector performance & software tools/Detector integration with MDI, Tuesday 19-Oct-2010, 16:00 - 18:30

• Status: submitted 22-Sep-2010, accepted 6-Oct-2010

• Abstract:
An algorithm to find and reconstruct $\tau$ leptons was developed, which targets $\tau${\scriptsize s} that produce high energetic, low multiplicity jets as can be observed at multi TeV e$^+$e$^-$ collisions. However, it makes no assumption about the decay of the $\tau$ candidate thus finding hadronic as well as leptonic decays. The algorithm delivers a reconstructed $\tau$ as seen by the detector which is not corrected for missing energy.

### b-tagging of high energy jets at CLIC: Issues and requirements

• Speaker: Marco Battaglia (University of California, Santa Cruz and CERN)

• Session: Detector Performance & software tools/Detector integration with MDI, Thursday 21-Oct-2010, 9:00 - 10:30

• Status: submitted 28-Sep-2010, accepted 6-Oct-2010

• Abstract:
The tag of high energy b-jets in multi-TeV e+e- collisions with high efficiency is important for searches and precision studies. The talk discusses preliminary requirements in terms of track extrapolation resolution and angular coverage and issues which are specific to TeV-scale b-jets.

### CLIC detector benchmarks

• Speaker: Frederic Teubert (CERN)

• Session: Detector Performance & software tools/Detector integration with MDI, Thursday 21-Oct-2010, 9:00 - 10:30

• Status: submitted 22-Sep-2010, accepted 6-Oct-2010

• Abstract:
In order to demonstrate the performance of the CDR proposed detector(s) design for a multi-TeV linear collider, a few physics processes have been selected as example. The main criteria in this selection was to cover complementary aspects of the detector performance, as well as to constitute a plausible physics scenario after the LHC initial results.

### Particle Flow Calorimetry at High Energies

• Speaker: Mark Thomson (University of Cambridge)

• Session: Detector Performance & software tools/Detector integration with MDI, Thursday 21-Oct-2010, 14:00 - 15:30

• Status: submitted 28-Sep-2010, accepted 6-Oct-2010

• Abstract:
The performance of particle flow calorimetry for a multi-TeV lepton collider such as CLIC have been studied in the context of the PandoraPFA algorithm. The optimisation of the algorithm for high energies will be discussed and it is shown that a jet energy resolution of better than 4 % can be achieved for jets in the energy range 45 GeV - 1.5 TeV. The evolution with energy of the different contributions to the jet energy resolution will be discussed.

### GEAR Extension: 3D Volume Tree, Events Generation with WHIZARD, and Mass Production using ILCDIRAC

• Speaker: Stephane Poss (CERN)

• Session: Detector performance & software tools/Detector integration with MDI, Tuesday 19-Oct-2010, 16:00 - 18:30

• Status: submitted 22-Sep-2010, accepted 6-Oct-2010

• Abstract:
This presentation will be divided in three parts: the first will give detail about providing access to a 3D volume representation implemented at reconstruction time that gives for example material budget information. The second part of the presentation will discuss the CLIC event generation using WHIZARD, the generator based on Omega. Finally, the mass production system ILCDIRAC, based on the DIRAC framework, will be presented with a summary of performances: number of events generated, number of concurrent jobs, etc.

### ILD and SiD Detector Concepts for CLIC

• Speaker: Christian Grefe (CERN and University of Bonn)

• Session: Detector Performance & software tools/Detector integration with MDI, Thursday 21-Oct-2010, 14:00 - 15:30

• Status: submitted 22-Sep-2010, accepted 6-Oct-2010

• Abstract:
The International Large Detector concept (ILD) and the Silicon Detector concept (SiD) were developed for the International Linear Collider (ILC) and have been validated after being presented in their respective letters of intent. Because of the higher center of mass energy, differences in the beam-induced-background as well as the challenging beam structure at CLIC, several modifications are necessary in order to make them viable detector concepts also for CLIC. The modified concepts, which will be used for the CLIC CDR studies, will be presented.

## Higgs and Supersymmetry

### Determination of Heavy Slepton Mass at CLIC

• Authors: Jean-Jacques Blaising (LAPP Annecy), Marco Battaglia (University of California, Santa Cruz and CERN)

• Speaker: Jean-Jacques Blaising (LAPP Annecy)

• Session: Higgs, SUSY, Cosmology, Thursday 21-Oct-2010, 9:00 - 10:30

• Status: submitted 15-Sep-2010, accepted 6-Oct-2010

• Abstract:
The determination of smuon and neutralino masses in smuon pair production is an important part of the program of spectroscopic studies of Supersymmetry at a high energy linear collider. We report preliminary results of a study of e+e- -> ~e+_R ~e-_R and e+e- -> ~mu_R+ ~mu_R- in a high-mass, cosmology-motivated Supersymmetric scenario at 3 TeV at CLIC. These processes are good examples to study requirements on the beam energy spectrum and polarisation and the track momentum and energy resolution in a simple final state. We discuss the expected accuracy on the mass measurements as a function of the momentum/energy resolution, luminosity spectrum, beam polarisation and time stamping capability. Results obtained at generator level are validated by comparison to full simulation and reconstruction. Preliminary requirements for the detector performances and beam polarisation are presented.

### A Study of e+e- -> H0A0 -> bbbb at 3 TeV at CLIC

• Authors: Marco Battaglia (University of California, Santa Cruz and CERN), Frederik Bogert (University of California, Santa Cruz and CERN), Pamela Ferrari (NIKHEF)

• Speaker: Marco Battaglia (University of California, Santa Cruz and CERN)

• Session: Higgs, SUSY, Cosmology, Thursday 21-Oct-2010, 11:00 - 12:30

• Status: submitted 15-Sep-2010, accepted 10-Oct-2010

• Abstract:
The precise determination of the masses of the CP-odd and -even heavy Higgs bosons is an important part of the study of Supersymmetry and its relation with cosmology through dark matter. We present a determination of the A0 boson mass with the e+e- -> H0A0 -> b b b b process for two dark matter motivated cMSSM scenario with M(A) = 906 and 1141 GeV respectively at CLIC. The analysis is performed with full simulation and reconstruction at 3 TeV accounting for beamstrahlung effects. SM and SUSY backgrounds are considered and the effect of the overlay of gamma gamma -> hadrons events on the signal is studied for various assumptions for the detector time-stamping capabilities. The di-jet mass resolution is improved by applying a kinematic fit. Requirements on parton energy resolution, b-tagging efficiency and time stamping capabilities are discussed.

### A Study of Chargino and Neutralino Masses using W and h energy spectra and threshold scans at CLIC

• Authors: Natali Alster (University of California, Santa Cruz), Marco Battaglia (University of California, Santa Cruz and CERN), Jean-Jacques Blaising (LAPP Annecy)

• Speaker: Natali Alster (University of California, Santa Cruz)

• Session: Higgs, SUSY, Cosmology, Thursday 21-Oct-2010, 9:00 - 10:30

• Status: submitted 15-Sep-2010, accepted 6-Oct-2010

• Abstract:
We present preliminary results on the anticipated accuracy for the determination of chargino and neutralino masses in cMSSM scenarios at CLIC. We study decays involving W and h bosons and compare the precision achievable through the analysis of the boson energy distributions to that of a dedicated threshold scan taking into account beamstrahlung. This study highlights requirements on the parton energy resolution and the luminosity of the accelerator at different centre-of-mass energies between 1.5 and 3 TeV.

### A Study of Light-flavored SQuark Production at CLIC

• Authors: Peter Schade (DESY and CERN), Frank Simon (MPI Munich)

• Speaker: to be decided

• Session: Higgs, SUSY, Cosmology, Wednesday 20-Oct-2010, 16:00 - 18:30

• Status: submitted 4-Oct-2010, accepted 6-Oct-2010

• Abstract:
A multi-TeV linear e+e- collider is an ideal tool for precise studies of the masses of squarks. In scenarios where the gluino is heavier than the squarks, light-flavored right-squarks will decay almost exclusively into the corresponding quark and the lightest neutralino, leading to simple event topologies which offer excellent possibilities for clean mass measurements.

We discuss different techniques for the squark mass measurement and evaluate their performance at the 3 TeV CLIC e+e- collider in a fast analysis study. For this, signal and background events were generated including initial state radiation and the beam energy spread due to beamstrahlung. The detector performance was modelled by acceptance cuts and an empirical jet energy smearing. First signal selection studies using simple cuts as well as a likelihood technique have been performed. A full simulation study, based on this fast simulation, is in preparation for the CLIC CDR.
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Topic revision: r11 - 2010-10-16 - MichaelHauschild

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